This invention relates generally to engines, and more particularly to common rail fuel injection systems that use a common electrical actuator(s) to control multiple fuel injectors.
Common rail fuel injection systems are becoming more widespread for use with diesel engines. One example of such a fuel injection system is shown and described in U.S. Pat. No. 5,133,645, which issued to Crowley et al. on Jul. 28, 1992. Crowley et al. includes an electronic control module and an electronic distribution unit which control a plurality of high pressure fuel supply pumps and fuel injectors. As with other traditional common rail fuel injection systems, each of the fuel injectors included in the Crowley et al. fuel injection system includes its own individual electrical actuator. In this and other common rail fuel injection systems, the individual electrical actuators must cooperate to ensure that the proper amount of fuel is injected from each injector at the proper time. While the Crowley fuel injection system has performed adequately, there is room for improvement. For instance, if the number of electrical actuators, or solenoids, could be reduced, this could benefit the fuel injection system in a number of ways. First, because the number of parts has been reduced, there are less parts that can fail during system operation and hinder system performance. Additionally, injector performance variability might be reduced. Any reduction in the number of moving and/or electrical components should improve system robustness.
The present invention is directed to overcoming one or more of the problems as set forth above.
In one aspect of the present invention, a fuel injector comprises an injector body with a needle control chamber disposed therein. A direct control needle valve is at least partially positioned in the injector body and includes a closing hydraulic surface exposed to fluid pressure in the needle control chamber. The fuel injector also comprises an unobstructed high pressure passage extending between the needle control chamber and outside the injector body. Also, the fuel injector comprises an unobstructed low pressure passage extending between the needle control chamber and outside the injector body.
In another aspect of the present invention a method of injecting fuel comprises the steps of opening a nozzle outlet of a fuel injector at least in part by relieving pressure on a closing hydraulic surface of a direct control needle valve. Restricting fuel flow to the nozzle outlet at least in part by positioning a flow restriction valve member in a first position. Unrestricting fuel flow to the nozzle outlet at least in part by positioning said flow restriction valve member in a second position. Finally, closing the nozzle outlet at least in part by increasing pressure on the closing hydraulic surface of the direct control needle valve.
In yet another aspect of the present invention, a fuel injection system comprises a high pressure fuel rail and a low pressure fuel drain. Also, the fuel injection system comprises a plurality of fuel injectors that each include a direct control needle valve and a common electrical actuator coupled to the plurality of fuel injectors.